Recorder for radio locators



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RECORDER FOR RADIO LOCATORS Filed Aug. 30, 1943 2 Sheets-Sheet 2 Patented Feb. 181947 RECORDER FOR RADIO LOCATOBS Irving Wollt, Princeton, N. J., assigner to Radio Corporation of America,

Ware

a corporation of Dela- Application August 30, 1943, Serial No. 500,739

1o claims. l

My invention relates to radio locator systems and to methods of and means for recording the object location infomation received by an object locator system.

An object of the invention is to provide an improved method of and means for recording radio locator information.

Another object of the invention is to provide an improved method of and means for recording radio locator information on a low speed recorder such as a facsimile recorder.

Still another object of the invention is to provide an improved method of and means for obtaining a record that indicates clearly the location of objects to the right and to the left of the radio locator system.

In one embodiment of the invention, the radio locator is of the pulse-echo type having either a transmitter or a receiver that is switched alternately to a pair of antennas that have directivity to the right and to the left, respectively. The reected pulses are applied to a cathode ray indicator tube which has its time sweep axis displaced in the vertical direction synchronously with the left-right antenna switching. The resulting right and left images on the screen of the indicator tube are projected by means of a suitable lens system, upon the mosaic screen of a cathode ray storage tube. The stored images are 1 then reconverted to electrical signals by scanning the storage mosaic slowly with an electron beam. These signals are supplied to a recorder in which the scanning is synchronous with the scanning of the storage mosaic.

Preferably, the scanning of the storage mosaic is in opposite directions for the right and left images so that they may be recorded to the right and to the left, respectively, of a center line on the record representing zero distance.

The invention will be better understood from the following description taken in connection with the accompanying drawings in which Figure 1 is a circuit and block diagram of a pulse-echo system embodying my invention,

Figure la is a View of the screen end of the cathode ray indicator tube shown in Fig, l,

Figurelb is a view of the'record that is obtained when the image on the indicator tube is as shown in Fig. la, and

Figure 2 is a view in perspective of the cathode ray indicator and storage tubes which shows the direction of scanning in the two tubes.

In the several figures, similar parts are indicated by similar reference characters.

Referring to Fig. 1 of the drawings.' a high fre-V quency radio transmitter I Il is pulse modulated by means of a pulse modulator II'and a pulse generator I2 to radiate short radio pulses alternately to the right and to the left from a pair of antennas I3 and I4, respectively. The transmitter pulses may also be applied over a conductor I6 to a receiver to function as initial or time reference pulses. The keying or modulating pulses preferably are applied to the keyer I I through a delay circuit I5. The antennas I3 and I6 may be two dipoles in parabolic reflectors whichrare positioned to radiate to the right and to the left. The antennas I3 and IB are connected alternately to the transmitter by means of suitable leftright switching means I1 which may be driven by a motor (not shown). The transmitted pulses may occur at the rate of 1700 per second and have a duration of 0.3 Vmicro-seconds; the switching from left to right may occur at the rate of 30 per second, that is, on leitl for Vm second and on right for 1/60 second. I'hese values are given merely by way of example.

The reflected pulses are picked up by a suitable antenna I8 and supplied to the receiver I9 which amplies and demodulates them. They are then applied with positive polarity to the control grid 2I of a cathode ray tube 22 which is biased near electron beam cut-o.

The cathode ray tube 22 may be of conventional design having a uorescent screen 2t and two pairs of defiecting plates 24 and 2t positioned at right angles to each other. A sawtooth sweep or timing voltage is produced by a sawtooth generator 2l and applied to the plates 2t to deflect the cathode ray horizontally at a repetition rate of 1700 sweeps per second in the example being described.

A relay switch arm 2B is operated synchronous- 1y with the left-right antenna switching to apply voltage from a battery 29 to the deflecting plates 2t whereby the cathode ray of the tube 22 is defiected up or down to give an upper image of reiiecting objects to the right when the antenna radiation is toward the right and to give a lower image oi reiiecting objects to the left when the antenna radiation is toward the left. Such images are illustrated in Fig. la where objects A and B to the right and an object C to the left are indicated.

Preferably, the horizontal scanning line is widened, in effect, by also applying to the vertical deflecting plates 26 a high frequency sine wave voltage from a suitable source 3i.

.In order to record the reflecting object indications that appear on the iiuorescent screen 23,

the "right and leit" images are projected by means of a suitable lens system 32v upon a storage screen 33 of a cathode ray storage tube 34 such as a television pick-up tube of the low velocity beam type. Thus the images are stored on the screen 33 whereby they may be scanned slowly enough to obtain a signal that can be recorded on a comparatively slow speed recorder.

Referring brieily to the structure of the tube 34, the tube has a. low velocity beam gun comprising a cathode 3B, a control grid 31, a first anode 39 and a second anode 4I. Ring electrodes 42 and 43 are provided to slow down the electron beam as it approaches the storage screen 33. In the example illustrated, the signal taken off the screen 33 by the low velocity beam appears across an output resistor 44 which is connected between the back plate of the screen 33 and ground. The horizontal and vertical deilections of the low velocity beam maybe obtained by means of two pairs of deflecting coils H and V, respectively.

The stored image on the mosaic 33 is scanned by means of a triangular current wave, repre.

sented by the graph 45, which is supplied to the horizontal deecting coils H. In order to scan the right and left indications alternately, rectangular pulses of current are supplied to the verticaldefleeting coils V from a battery 46 through a switch arm 41 operated by a cam 43. The direction of scanning is indicated in Fig. 2 by the arrows on the dotted line 49, the scanning being in one direction across the right indications and in the opposite direction across the left indications.

A high frequency sine wave deilecting current is also supplied to the vertical defiecting coils V from an oscillator 5| The output of oscillator 5I is applied between ground and the center point of the battery 46 through a transformer 52. The purpose of this sine wave deilection is to provide a wide scanning path for the electron beam so that the image spots will be completely scanned.

The recorder indicated at 53 may be of a type commonly employed in facsimile systems. In the example illustrated, it is a carbon paper recorder comprising a drum 54 having a spiral scanning strip thereon and having a printer bar (not shown) which is actuated by the output signal of the storage tube 34 after suitable amplication by a direct-current amplifier 56.

The triangular scanning wave 45 is produced by means of a potentiometer 51 comprising a resistor 58 and an arm 59 that is rotated in synchronism with and at the same rate as the recorder drum 54 at the rate of one-half revolution per second, for example. The potentiometer resistor 58 has its two halves connected in parallel with respect to a battery 6I whereby the deiiecting current supplied from the arm 59 increases and then decreases as the arm is rotated to produce the triangular current wave 45. The mechanical coupling of the scanning drum and the potentiometer arm is such that the recorder scans the left half of a paper strip 62 while the left image indications on the mosaic are being scanned in one direction and scans the right half of the paper while the "right image indications on the mosaic are being scanned in the opposite direction. As a result the recorded image is of the character shown in Fig. 1b where the distances to objects at the right or at the left of the locator system are measured from the center or zero line of the paper strip 62.

In some cases it may be desirable to record only the signal reiiected from one of the directions of signal transmission and/or reception,

For example, there may be a faint mark on the right side of the paper strip 52 that is so poorly dei-ined that it is difficult to determine whether it was made by a signal reected from the right or caused by an irregularity in the recorder such as an irregularity in the scanning spiral or in the printer bar. Since such an irregularity probably would not be duplicated on the other half of the scanning spiral or printer bar, a check can be made as to whether the faint mark represents a signal by recording the signal reflected from the right upon both the right and left sides of the paper strip to see whether the mark is also recorded on the left side of the paper, which would indicate that a reflected signal caused the mark.

The above described check can be made while continuing to radiate signal in a plurality of directions successively (in the directions left and right in the example illustrated) by holding the switch arm 41 against either the upper switch contact point or against .the lower switch contact point during at least one cycle of triangular deflection, the position of the switch 41 depending upon whether it is the left or right signal that is to be recorded. Thus thecathode ray of the storage tube is caused to scan back along the same path that it just traced. In the particular design shown in Fig. 1, the switch 41 may be thrown manually to either its upper or lower position by mechanically disconnecting the cam 48 from the motor drive and then tuning the cam manually to the desired switch position.

It will be apparent that the invention is not limited to the specific left-right antenna switching arrangement that has been illustrated. For example, a rotating directive antenna might be utilized as illustrated in application Serial No. 500,737, filed on the same day as the present application, now issued as Patent No. 2,403,562, on July 9, 1946, and entitled Recorder for radar system; that is, a sharply directive continuously rotating antenna might be switched to radiate to the right while rotating through about 10 degrees and to next radiate to the left while rotating through about 10 degrees.

It should be understood that the desired antenna directivty may be obtained by the receiving antenna system if desired, rather than by the 50 transmitter antenna system. For example, the

left-right antennas corresponding to antennas I4 and I3 may be a pair of directive receivery antennas that are switched successively and the transmitter antenna system may then be nondirective.

I claim as my invention:

l. A radio locator system comprising means for transmitting a periodically modulated radio wave toward a reilecting object, a radio receiver for receiving the wave reflected fromisaid object, an electron beam tube having a surface upon which a signal may be stored, means including said electron beam tube for converting said received wave to a stored signal on said surface, and means for scanning said stored signal at a slow rate compared with that of said periodic modulation to produce a signal that can be recorded, a recorder which includes scanning means, means for supplying said last-mentioned signal to the recorder, and means for synchronizing said slow scanning of said image with the recorder scanning.

2. A radio locator system comprising means for transmitting recurring pulses of radio energy toward a reflecting object, means for receiving the atrapar redected pulses, an electron beam tube having a surface upon which a signal may be stored, means for storing signals corresponding to said reflected pulses along a distance axis on said surface, and means for scanning said stored signal at slow rate compared with the rate of recurrence of said pulses to produce asignal that can be recorded, a recorder which includes scanning means, means for supplying said last-mentioned signal to the recorder, and means for synchronizing said slow scanning of said image with the recorder scanning.

3. A radio locator system comprising means ior transmitting a periodically modulated radio wave toward a reflecting object, a radio receiver for receiving the wave reected from said object, an electron beam tube having a surface upon which an image may be formed, means including said electron beam tube for converting said received wave to an image on said screen indicating the distance to the reflecting object, said converting means also including means for deflect ing said cathode ray at a comparatively high repetition rate, cathode ray tube means for scanning said image at a comparatively slow rate to produce a signal that may be recorded, a recorder which includes scanning means, means for suppiying said signal to the recorder, and means for synchronizing said slow scanning of said image with the recorder scanning.

li. A radio locator system comprising means for transmitting a pulse modulated radio wave toward a reecting object, a radio receiver for receiving the wave reflected from said object, a cathode ray tube having a screen upon which an image may be formed, means including said cathode ray tube for obtaining from said received wave an image on said screen representative of the distance to and the position of the reiiecting object, saidA last means also including means for deecting said cathode ray at a comparatively high repetition rate, cathode ray tube means for scanning said image at a comparatively slow rate to produce an image signal that may be recorded on a comparatively low speed recorder, a recorder which includes scanning means,

and means for synchronizing said slow scanning of said image with the scanning of said recorder.

5. A radio locator system comprising means fortransmitting a periodically modulated radio wave toward a reflecting object, a radio receiver for receiving the wave reected from said object, a cathode ray tube having a screen upon which an image may be formed, means including said cathode ray tube for the reception of said reiiected waves an image on said screen indicating the distance to the reecting object, said last means also including means for deecting said `cathode ray at a comparatively high repetition rate, cathode ray tube means for scanning said image at a comparatively slow rate to produce an image signal that may be recorded on a comparatively slow speed recorder, a recorder which includes scanning means, means for applying said image signal to said recorder, and means for synchronizing said slow scanning of said image with the scanning of said recorder.

6. A radio locator system comprising means for transmitting radio wave pulses in two directions H toward reflecting objects, a radio receiver for receiving the waves reflected from said objects, a cathode ray tube having a screen upon which an image may be formed, means including said cathode ray tube for producing in response to the reception of said reflected waves two images on said screen representative of reflecting objects insaid two directions, respectively, which indicate the distances to the reiiecting objects, said last means also including means for deecting rsaid cathode ray at a comparatively high repetition rate, cath- -ode ray tube means for scanning said two images at a. comparatively slow rate and in opposite directions, respectively, to produce image signals that may be recorded, a recorder which includes means for scanning in only one direction during said scanning of the two images, means for applying said image signals to said recorder, and means for synchronizing said slow scanning of said image with the scanning of said recorder.

7. A radio locator system comprising means for transmitting a periodically modulated radio wave alternately to the left .and to the right toward reecting objects,` a radio receiver for receiving the waves reiiected from said objects, a cathode ray tube having a screen upon which an image may be formed, means including said cathode ray tube for producing in response to the reception of said reflected waves images on said screen representative of reecting objects to the 4left and to the right which indicate the distance to the reecting objects, said last means also including means for deflecting said cathode ray at a comparatively high repetition rate, cathode ray tube means for scanning said left and right images at a comparatively slow rate and in opposite directions to produce image signals that may be recorded, a recorder which includes means for scanning in only one direction during said scanning of the left and right images, means for applying said image signals to said recorder, and

means for synchronizing said slow scanning oi said image with the scanning of said recorder.

8. A radio locator system comprising means for transmitting a pulse modulated radio wave alternately to the left and to the right toward reecting objects, a radio receiver for receiving the waves reected from said objects, a cathode ray tube having a fluorescent screen, means including said cathode ray tube for producing in response to the reception of said reflected waves images on said screen representative of reflecting objects to the left and to the right which indicate the distance to the reflecting objects, said last means also including means for deflecting said cathode ray at a comparatively high repetition rate, a cathode ray storage tube having a storage mosaic, means for projecting said images upon said storage mosaic, means for scanning the left and right images 0n said mosaic at a comparatively slow rate and in opposite directions to produce image signals that may be recorded, a recorder which includes means for scanning in only one direction during said slow scanning ci the left and right images, means for applying said image signals to said recorder, and means for synchronizing said slow scanning of said image with the scanning of said recorder.

9. A radio locator having a, directive antenna system, means for transmitting a pulse-modulated radio wave toward reflecting objects, means for receiving the reiiected waves from a plurality of directions in sequence, said last means including switching means for switching directive antennas in said antenna, system at a rapid rate for supplying reflected waves to the receiver from said directions successively, means for producing and storing an electrical image representative of the distances to the reflecting objects in at least one of said directions, means for scanning said image at a slow rate compared with said switcha recorder,

amasar obtain a signal that may be recorded,

means for supplying said last-mentioned signal to said recorder, and means for synchronizing the scanning of said recorder with said slow scanning of said image.

10. A radio locator having a directive antenna system, means for transmitting a pulse-modulated radio wave toward reflecting objects, means for receiving the reflected waves from a plurality of directions in sequence, said last means includlng switching means for successively switching directive antennas in said antenna system at a rapid rate for supplying reflected waves to the receiver from said directions, means for producing and storing an electrical image representative of the distances to the reflecting objects in a plurality of said directions, means for scanning said image at a slow rate compared with said switching rate to obtain a signal that may be ing rate to REFERENCES @ITED The following references are of record in the file of this patent:

UNTTED STATES PATENTS Number Name Date 1,660,886 Randall Feb. 28,1 1928 2,189,549 Hershberger Feb. 6, 1940 2,243,456 Dutter May 27, 1941 1,936,706 Ariel Nov. 28, 1933 2,234,329 Wol Mar. 11, 1941 2,189,549 Hershberger Feb. 6, 1940 2,291,476 Kernkamp July 28, 1942 

